Extractor Fan Ducting

27 Oct 2006
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United Kingdom
I am installing an extractor fan in my bathroom and having read the many threads on wiring fans I am now more than happy how to do it!

My issue is how best to fit the ducting. I want to install the fan in the bathroom ceiling and then fit the ducting in the loft space and take it horiontally out to the gable end wall.

Obvioulsly this means the flexible ducting I was going to use will take a 90 degree bend to get it out to the gable end wall. Will this work OK or will I need a condensation trap to stop any water dripping back down into the fan?

Any help much appreciated :rolleyes:
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The way i did was with a fan that had 2 extractor plates. One of them fitted in the bathroom ceiling, and the fan was then fitted in the loft, about half a meter higher, and horizontally. The rest of the flexible ducting then ran on a downwards slope to where i fitted the other extractor plate, venting the air outside.
Have you read the many threads on part p of the building regulations?

There are legal implications of this work which you must consider.
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The instructions tell you how to install the fan in either the wall, window or ceiling but nothing about ducting.
If you are thinking of condensation:

After the curve or elbow that turns the upwards spigot from the fan to the horizontal run to the wall, put a slight slope downwards towards the wall, then any condensation will not run back annoyingly towards the fan.

A duct made of smooth tube (like soil pipe) will trap less water and dust than the convoluted flexi duct, so resistant to mould.

Flop some loft insulation over the duct to prevent it being cold, that will minimise condensation, especially if you have a delay in turning off the fan after showering, so that it blows some warm (relatively) dry air through it after most of the steam hs gone.

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